Method of forming thin dielectric layers

Abstract

Atomic layer deposition of very thin dielectric metal oxide layers in manufacturing of semiconductor devices by ozone oxidation of precursor monolayers leads to unacceptable impurity content and leakage current of the layers. It is proposed to perform precursor oxidation by means of radicals generated by oxidizing and reductive gases, which are simultaneously fed into the reaction vessel. This way very low impurity content and leakage current is achieved even in very thin (several nm) layers.

1 . A method of forming a metal oxide layer on a substrate residing in a processing vessel, the method comprising: 
 a) exposing the surface of a substrate to a precursor compound of a metal in gaseous form and allowing molecules of said precursor to adsorb on said surface;    b) exposing said surface to a first inert purging gas, thereby removing from said surface molecules of said precursor;    c) exposing said surface to radicals containing oxygen, thereby converting said metal compound precursor into metal oxide, wherein an oxidizing gas containing O 2 , N 2 O, NO, and/or NO 2 , and a reductive gas containing H 2 , NH 3 , and/or CH 4 , are supplied simultaneously by separate supply systems into said processing vessel and the pressure in the vessel is being kept low enough to avoid rapid reaction of said oxidizing and reductive gases;    d) exposing said surface to a second purging gas, thereby removing oxidation products other than the metal oxide from said surface; and    e) repeating steps a) through d) until the desired thickness of the metal oxide is achieved.    
   
   
       2 . The method of  claim 1 , wherein the radicals containing oxygen are oxygen or hydroxyl radicals.  
   
   
       3 . The method of  claim 1 , wherein the oxidizing gas is oxygen.  
   
   
       4 . The method of  claim 1 , wherein the reductive gas is hydrogen.  
   
   
       5 . The method of  claim 1 , wherein the exposing of step b) removes from said surface any molecules of said precursor, which are in excess of a monomolecular layer.  
   
   
       6 . The method of  claim 4 , wherein the molar ratio of hydrogen to oxygen is 2 or less.  
   
   
       7 . The method of  claim 6 , wherein the molar ratio of hydrogen to oxygen is in the range from 0.1 to 1.  
   
   
       8 . The method of  claim 1 , wherein the metal is aluminum.  
   
   
       9 . The method of  claim 8 , wherein the precursor is aluminum trimethyl or triethyl.  
   
   
       10 . The method of  claim 1 , wherein the metal is hafnium.  
   
   
       11 . The method of  claim 10 , wherein the precursor comprises a material selected from the group consisting of hafnium tetrachloride, tetrakis(diethylamido)hafnium, tetrakis(methylethylamido)hafnium, tetrakis(dimethylamido)hafnium, tetrakis(t-butoxy)hafnium, and tetrakis(ethoxy)hafnium and combinations thereof.  
   
   
       12 . The method of  claim 1 , wherein the metal comprises at least one metal selected from the group consisting of tantalum, titanium, niobium, zirconium, molybdenum, indium, tin, tungsten, silicium, and the rare earth metals.  
   
   
       13 . The method of  claim 1 , wherein the pressure during step c) is in the range from 13 to 260 Pa.  
   
   
       14 . The method of  claim 13 , wherein the pressure during step c) is in the range from 39 to 130 Pa.  
   
   
       15 . The method of  claim 1 , wherein the temperature during step c) is in the range from 250 to 500° C.  
   
   
       16 . The method of  claim 15 , wherein the temperature during step c) is in the range from 300 to 400° C.  
   
   
       17 . The method of  claim 15 , wherein the temperature during step c) is in the range from 350 to 400° C.  
   
   
       18 . A method of forming a layer of aluminum oxide on a substrate residing in a processing vessel, the method comprising: 
 a) exposing the surface of the substrate to a precursor compound of aluminum in gaseous form and allowing molecules of said precursor to adsorb on said surface;    b) exposing said surface to a first inert purging gas, thereby removing from said surface molecules of said precursor;    c) exposing said surface to radicals containing oxygen, thereby converting said aluminum compound precursor into aluminum oxide, wherein oxygen and hydrogen are supplied simultaneously by separate supply systems into said processing vessel and the pressure in the vessel is low enough to avoid detonation of said oxidizing and reductive gases;    d) exposing said surface to a second purging gas, thereby removing oxidation products from said surface; and    e) repeating steps a) through d) until a desired thickness of the aluminum oxide is achieved.    
   
   
       19 . The method of  claim 18 , wherein the molar ratio of hydrogen to oxygen is 2 or less.  
   
   
       20 . The method of  claim 18 , wherein the exposing of step b) removes from said surface any molecules of said precursor, which are in excess of a monomolecular layer.  
   
   
       21 . The method of  claim 19 , wherein the molar ratio of hydrogen to oxygen is in the range from 0.1 to 1.  
   
   
       22 . The method of  claim 18 , wherein the pressure during step c) is in the range from 13 to 260 Pa.  
   
   
       23 . The method of  claim 22 , wherein the pressure during step c) is in the range from 39 to 130 Pa.  
   
   
       24 . The method of  claim 18 , wherein the temperature during step c) is in the range from 300 to 400° C.